鄂尔多斯盆地西南部上古生界流体包裹体特征及其意义

Characteristics and Significance of Fluid Inclusions in Upper Paleozoic of Southwest Ordos Basin

通过单偏光、荧光显微镜观察和显微冷热台测温等方法，对鄂尔多斯盆地西南部16口井24块上古生界砂岩样品进行全面的流体包裹体分析，归纳山西组和盒8段内主要含气层段流体包裹体岩相学特征，将不同包裹体组合内与烃类包裹体伴生的盐水包裹体均一温度、冰点温度等参数对比分析，结合研究区埋藏史推测致密砂岩储层内天然气的充注期次。测试结果显示与气态烃包裹体伴生的盐水包裹体均一温度范围为100～170℃，均一温度和冰点温度均未显示明显间断，表明储层内天然气运移是在中侏罗世一早白垩世内（200～100Ma）持续进行；愈合微裂隙内高气液比气态烃包裹体的气相组分以CH4为主，与其伴生盐水包裹体均一温度介于140～170℃之间，表明储层内天然气大量富集期为早白垩世（155～100Ma）；流体包裹体组合、均一温度及其地球化学组分测试结果综合分析认为，鄂尔多斯盆地西南部上古生界天然气运移富集是一个相对漫长且连续的过程，并以早白垩世为主要充注期。

With methods of polarizing and fluorescence microscope observation, micro-thermometry etc. , fluid inclusions of 24 Upper Paleozoic sandstone samples from 16 wells in southwest Ordos Basin were com- prehensively tested in this paper. On the basis of research on burial history,petrographic characteristics of fluid inclusions and homogeneous temperature,ice point temperature of associated aqueous inclusions from main production layers in Shanxi Formation and He 8 section,charging periods of natural gas in tight reservoir of study area can be inferred. The results show as follows. Homogeneous temperature of aqueous in clusion,associated with gaseous hydrocarbon,were 100-170℃. Homogeneous temperature and ice temperature show normal continuous distribution,which means the gas charging happened during Middle JurassicEarly Cretaceous（200-100Ma）. Component of gas inclusion in healed micro-crack is mainly CH, ,homogene ous temperature of aqueous inclusion, associated with gaseous hydrocarbon, was 140-170℃,which means the mainly gas charging occurred during Early Cretaceous（155-100Ma）. It is concluded that Paleozoic gas accumulation in the study area is a continuous and slow process, and the main charging period is Early Cretaceous.